A furnace such as a reverberatory furnace is used in molten metal processing. The furnace includes a main hearth where ingots and/or sows of solid articles of metal to be melted are placed on a sill from which they move into the hearth when melted. The hearth is heated by gas burners, for example. Some furnaces circulate the molten metal in the furnace, for example, using pumps of the types supplied by High Temperature Systems, Inc. Circulation of the molten metal is advantageous in that the molten metal is maintained at a more uniform composition and temperature; also, less heat may be required to maintain the molten metal temperature.
Various devices are used to transfer molten metal out of the furnace. Some furnaces include an opening for tapping the metal of the furnace. This can be hazardous and difficult as the opening may not remain clean over time and may not be sealed effectively.
An effective device is the unique patented Chameleon™ pump supplied by High Temperature Systems, Inc. as disclosed in U.S. Pat. Nos. 7,507,365 and 7,687,017, which are incorporated herein by reference. This is a multifunctional pump that moves an impeller inside an impeller chamber directing the molten metal to different outlets, permitting circulation, transfer or both, using a single pump. A stationary riser extends from the pump to a vessel located outside the furnace, such as above a ladle or crucible. When the pump moves the impeller to transfer mode, the molten metal leaves the pump, travels along the riser and enters the vessel. Circulation could occur simultaneously with the transfer, or at different times.
Molten Metal Equipment Innovations Inc. disclosed pump systems to achieve molten metal transfer from the furnace (see U.S. Pat. Nos. 9,205,490; 8,337,746; and 9,156,087) but they require substantial furnace down time to install. The furnace must be emptied and cooled. Then a separate chamber is constructed adjacent the furnace. A dedicated transfer pump is disposed in the chamber to enable transfer of molten metal from the furnace. This system is disadvantageous in view of the substantial loss in metal processing due to the furnace down time and the cost of constructing another chamber made of refractory. Most importantly, this system is limited in that the pump that is used cannot also carry out circulation but is limited to only molten metal transfer.